© Copyright 2008 STI INNSBRUCK Semantic Web Services Web Service Execution Environment (WSMX) Lecture VIII – 7 th May 2009 Srdjan Komazec

Where are we? #DateTitle 15 th MarchIntroduction 212 th MarchWeb Science 319 th MarchService Science 426 th MarchWeb Services (WSDL. SOAP, UDDI, XML) 52 nd AprilWeb 2.0 and RESTful services 623 rd AprilWSMO 730 th AprilWSML 87 th MayWSMX 914 th MayOWL-S and others 1028 th MayWSMO-Lite, MicroWSMO 114 th JuneSWS Use Cases 1218 th Juneseekda: the business point of view 1325 th JuneMobile services 142 nd JulyExam Preparation

Agenda Motivation –Semantically Enabled Service-oriented Architecture (SESA) Introduction –Relation to the WSMO and WSML –Design principles –Lifecycle Web Service Execution Environment (WSMX) –Architecture –Components –System entry points –Execution semantics Illustration by larger example 3

Service Orientation –Service-Oriented Computing (SOC) Services as the fundamental elements for the development of rapid, low-cost, and easily integrable enterprise applications, –Service-Oriented Architecture (SOA) SOC can be abstractly implemented by SOA, From function to object to service, SOA requirements: loose coupling, implementation neutrality, flexible configuration, long lifetime, granularity and teams. Existing technologies and SOA solutions are… –… difficult to scale without a proper degree of automation, –… partial solution to interoperability. SESA represents SOA empowered by adding semantics as a means to deal with heterogeneity and mechanization of service usage. 4 Motivation Semantically Enabled Service-oriented Architecture

Application of SESA offers a scalable integration, more adaptive to changes –service offerings and required capabilities are described by semantically rich and formal service models, –exchanged data is also semantically described, and –reasoning provides total or partial automation of tasks. A SESA implementation should build a layer on top of the existing technologies (e.g. Web Services). 5 Motivation Semantically Enabled Service-oriented Architecture WSMX is an implementation of SESA.

6 Motivation SESA Architecture Fensel, D.; Kerrigan, M.; Zaremba, M. (Eds): Implementing Semantic Web Services: The SESA Framework. Springer 2008.

7 Motivation Middleware for Semantic Web Services –Allows service providers to focus on their business, Reference implementation for WSMO –Eat our own cake, Environment for goal based discovery and invocation –Run-time binding of service requesters and providers, Provide a flexible Service Oriented Architecture –Add, update, remove components at run-time as needed, Keep open-source to encourage participation –Developers are free to use in their own code, and Define formal execution semantics –Unambiguous model of system behavior.

8 Introduction Relation to WSMO and WSML Conceptual Model & Axiomatization for SWS Formal Language for WSMO Ontology & Rule Language for the Semantic Web Execution Environment for WSMO SEE TC STI2 CMS WG

9 Introduction WSMX… … is comprehensive software framework for runtime binding of service requesters and service providers, … interprets service requester’s goal to – discover matching services, – select (if desired) the service that best fits, – provide data/process mediation (if required), and – make the service invocation, … is reference implementation for WSMO, … has a formal execution semantics, and … is service oriented, event-based and has pluggable architecture –Open source implementation available through Source Forge, –based on microkernel design using technologies such as JMX.

Service-oriented principle –Service reusability, loose coupling, abstraction, composability, autonomy, discoverability, Semantic Principle –Rich and formal description of information and behavioral models enabling automation of certain tasks by means of logical reasoning, Problem-solving principle –Goal-based discovery and invocation of services, and Distributed principle –Executing process across a number of components/services over the network, thus promoting scalability and quality of process. 10 Introduction Design principles

Lifecycle 1.Discovery - determines usable services for a request, 2.Composition - combine services to achieve a goal, 3.Selection - chooses most appropriate service among the available ones, 4.Mediation- solves mismatches (data, protocol, process) hampering interoperation, 5.Choreography – interactions and processes between the service providers and clients, 6.Grounding – lifting and lowering between the semantic and syntactic data representations, and 7.Invocation - invokes Web service following programmatic conventions. 11

WSMX Current middleware status 12

13 WSMX Components

WSMX Components Communication Manager, Invoker and Grounding Responsible for interaction with services and entities that are external to WSMX. Should be open to support as many transport and messaging protocols as possible (transparently to WSMX). WSMX uses –The SOAP implementation from Apache AXIS, and –The Apache Web Service Invocation Framework (WSIF). WSMO service descriptions are grounded to WSDL by the means of XSLT lifting and lowering Both RPC and Document style invocations possible 14 Network Invoker Apache AXIS Grounding Mediated WSML Data XML Web Service SOAP

15 WSMX Components Discovery Responsible for finding appropriate Web Services capable of fulfilling a goal Different techniques available –trade-off: ease-of-provision vs. accuracy –resource descriptions & matchmaking algorithms Key Word Matching - match natural language key words in resource descriptions, Controlled Vocabulary - ontology-based key word matching, and Semantic Matchmaking - what Semantic Web Services aim at. Ease of provisionPossible Accuracy

Allows for a fast filtering and ranking of the huge number of available services rather quickly. Nonfunctional properties from the Dublin Core namespace (e.g. dc#description) are candidates for indexing and querying. Dictionaries of synonyms (WordNet) can be used to discover more services. 16 WSMX Components Discovery – Key Word Matching wsmlVariant _" namespace {_" dc _" webService WSMuller nfp dc#title hasValue "Muller Web Service" dc#description hasValue "We ship to Africa, North America, Europe, Asia (all countries)." dc#contributor hasValue "Maciej Zaremba, Matt Moran, Tomas Vitvar, Thomas Haselwanter" endnfp capability WSMullerCapability...

17 WSMX Components Discovery – Simple Semantic Description Exact Match: G, WS, O, M ╞  x. (G(x) WS(x) ) PlugIn Match: G, WS, O, M ╞  x. (G(x) => WS(x) ) Subsumption Match: G, WS, O, M ╞  x. (G(x) <= WS(x) ) Intersection Match: G, WS, O, M ╞  x. (G(x)  WS(x) ) Non Match: G, WS, O, M ╞ ¬  x. (G(x)  WS(x) ) = G= WS X Keller, U.; Lara, R.; Polleres, A. (Eds): WSMO Web Service Discovery. WSML Working Draft D5.1, 12 Nov 2004.

One service which best satisfies the user preferences is selected from the candidate services returned by the service discovery. Selection –determines best candidate out of discovered WS, Ranking –determines a priority list of discovered WS. The process is run after “functional” discovery Criteria: –Quality of Service (security, robustness, availability), –Context (regional, business / social communities), –Preferences and policies, –Financial criteria, –… 18 WSMX Components Selection and Ranking

Ontology-to-ontology mediation A set of mapping rules are defined and then executed –Ontology Mapping Language Initially rules are defined semi-automatic Create for each source instance the target instance(s) 19 WSMX Components Data Mediation Fensel, D.; Kerrigan, M.; Zaremba, M. (Eds): Implementing Semantic Web Services: The SESA Framework. Springer 2008.

20 WSMX Components Data Mediation Design-time –Inputs Source Ontology and Target Ontology –Features Graphical interface Set of mechanism towards semi- automatic creation of mappings Capturing the semantic relationships identified in the process Storing these mappings in a persistent storage –Output Abstract representation of the mappings Run-time –Main Mediation Scenario: Instance Transformation –Inputs Incoming data –Source ontology instances –Features Completely automatic process Grounding of the abstract mappings to a concrete language –WSML Uses reasoner to evaluate the mapping rules –Outputs Mediated data –Target ontology instances

Requester and provider have their own communication patterns Only if the two match precisely, a direct communication may take place At design time equivalences between the choreographies’ conceptual descriptions is determined and stored as set of rules The Process Mediator provides the means for runtime analyses of two choreography instances and uses mediators to compensate possible mismatches 21 WSMX Components Process Mediation

22 WSMX Components Process Mediation Fensel, D.; Kerrigan, M.; Zaremba, M. (Eds): Implementing Semantic Web Services: The SESA Framework. Springer 2008.

Requester and provider have their own observable communication patterns –Choreography part of WSMO Choreography instances are loaded for the requester and provider –Both requester and provider have their own WSMO descriptions Abstract State Machines (ASM)-based Choreography Engine –Evaluation of transition rules prepares the available data –Sends data to the Process Mediator filters, changes or replaces data –Receives data from PM and forwards it to the Communication manager data to be finally sent to the communication partner 23 WSMX Components Choreography

Stores internal memory model to a data store Decouples storage mechanism from the rest of WSMX Data model is compliant to WSMO API Independent of any specific data store implementation i.e. database and storage mechanism Maintains six repositories to store –WSMO top level entities, i.e. Goals, Web Service descriptions, Mediators, and Ontologies. –Event data and intermediate messages –WSDL descriptions 24 WSMX Components Resource Manager

25 WSMX Components A Generic Framework for Reasoning with WSML Fensel, D.; Kerrigan, M.; Zaremba, M. (Eds): Implementing Semantic Web Services: The SESA Framework. Springer 2008.

Represent input ports to which messages can be sent for initiating specific execution semantics. –getWebServices(WSMLDocument): Web Services A service requester wishes to discover a list of SWS fulfilling its requirements provided by as a goal description using WSML. A set of WSML Web Service descriptions whose capability matches the goal is returned. –invokeWebService(WSMLDocument, Context): Context Used to invoke already known Semantic Web Service by relying on data provided in the form of WSML ontology and conversation context. –achieveGoal(WSMLDocument): Context A service requester wishes to use WSMX for all aspects of goal-based service invocation (discovery, mediation, invocation) by providing both goal and data in the single WSML document. Processing of the message is identified by the conversation context. 26 WSMX Entry Points

27 Execution Semantics

Execution Semantics Formal description of the operational behavior of the system in terms of computational steps –Greater flexibility in SESA implementations, –Foundations for model testing, –Executable representation, and –Improved model understanding among humans. Mandatory execution semantics –Goal-Based Web Service Discovery –Web Service Invocation –Goal-Based Service Execution 28

29 Execution Semantics Goal-Based Web Service Discovery Fensel, D.; Kerrigan, M.; Zaremba, M. (Eds): Implementing Semantic Web Services: The SESA Framework. Springer 2008.

30 Execution Semantics Web Service Invocation Fensel, D.; Kerrigan, M.; Zaremba, M. (Eds): Implementing Semantic Web Services: The SESA Framework. Springer 2008.

31 Execution Semantics Goal-Based Service Execution Fensel, D.; Kerrigan, M.; Zaremba, M. (Eds): Implementing Semantic Web Services: The SESA Framework. Springer 2008.

32 Illustration by larger example

The goal is to discover a suitable solution for the transportation of a package with defined size and weight Candidate Web Services have different constraints regarding the transportation destinations, package size and weight acceptance, as well as pricing schemas For more information visit: – 33 Illustration by larger example Scenario description

34 Illustration by larger example Goal description wsmlVariant _" goal GoalA1 capability GoalA1Capability postcondition definedBy ( ?x[sop#price hasValue ?price] memberOf sop#PriceQuoteResp and sop#isShipped(shipmentOrderReq) ). interface GoalA1Interface choreography GoalA1Choreography stateSignature GoalA1StateSignature in sop#ShipmentOrderReq out sop#ShipmentOrderResp transitionRules GoalA1TransitionRules forall {?request} with (?request memberOf sop#ShipmentOrderReq) do add(_#1 memberOf sop#ShipmentOrderResp) endForall ontology GoalRequest instance shipmentOrderReq memberOf sop#ShipmentOrderReq sop#from hasValue soi#MoonContactInfo sop#shipmentDate hasValue soi#shipmentDate1 sop#package hasValue package sop#to hasValue soi#SzyslakContactInfo instance package memberOf so#Package so#quantity hasValue 1 so#length hasValue 7.0 so#width hasValue 6.0 so#height hasValue 4.0 so#weight hasValue 1.0 instance shipmentDate1 memberOf so#ShipmentDate so#earliest hasValue " T13:00:00.046Z" so#latest hasValue " T13:00:00.046Z"

35 I want to have my package shipped from CA, USA to Tunis, Africa size (7/6/4), weight 1 lbs, the cheaper the better. Illustration by larger example AchieveGoal execution semantics

36 Goal expressed in WSML is sent to the WSMX Entry Point Illustration by larger example AchieveGoal execution semantics

37 Communication Manager instantiates AchieveGoal Execution Semantics Illustration by larger example AchieveGoal execution semantics

38 Discovery is employed in order to find suitable Web Service Discovery consults appropriate ontologies and Web Service descriptions Web Service may be invoked in order to discover service availability Illustration by larger example AchieveGoal execution semantics

39 List of candidate Web Services is ranked and best” solution is selected Illustration by larger example AchieveGoal execution semantics

40 Requester and provider choreographies are instantiated and processed Invocation of Web Service occurs Illustration by larger example AchieveGoal execution semantics

41 Result is returned to the client in the form of WSML message Illustration by larger example AchieveGoal execution semantics

Learning material Dieter Fensel, Mick Kerrigan, Michal Zaremba (Eds.), Implementing Semantic Web Services: The SESA Framework. Springer-Verlag, Charles Petrie, Tiziana Margaria, Holger Lausen, Michal Zaremba (Eds.), Semantic Web Services Challenge: Results from the First Year. Springer-Verlag, 2008 Online resources: – – 42

Next Lecture #DateTitle 15 th MarchIntroduction 212 th MarchWeb Science 319 th MarchService Science 426 th MarchWeb Services (WSDL. SOAP, UDDI, XML) 52 nd AprilWeb 2.0 and RESTful services 623 rd AprilWSMO 730 th AprilWSML 87 th MayWSMX 914 th MayOWL-S and others 1028 th MayWSMO-Lite, MicroWSMO 114 th JuneSWS Use Cases 1218 th Juneseekda: the business point of view 1325 th JuneMobile services 142 nd JulyExam Preparation

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